In highly automated driving, a monitoring of the setpoint trajectory calculated by the vehicle is essential for safety reasons before the vehicle drives along it. Usually, the situation is basically that the setpoint trajectory is checked for collisions with all detected objects. If a setpoint trajectory should lead to a collision, this trajectory would not be rated as a sensible choice, and would not be traveled. It is, however, generally difficult to determine an actual size, particularly a width and a length, of objects. Particularly surround sensors, such as a radar sensor or a mono camera, are normally at best able to recognize that an object is located somewhere within the visual range. Normally, the sensor is not able to determine the exact contour of the object. Thus, checking setpoint trajectories based on detected objects is difficult.
The aforementioned surround sensors are also not able to provide the information as to whether there actually exists nothing else all the way to the object. This is essentially due to the fact that usually object sensors are used. For this reason, in addition, active clearance sensors may also be used, which measure the clearance directly. Objects are an approximation of the entire “occupied space”, but do not really image it (because of the limited capabilities of the sensor). In particular, object sensors may overlook objects, which usually presents a great problem. When clearance sensors overlook a clearance, it is no problem from a safety technology point of view.